GB2120656A

GB2120656A - Preparation of thio-bis-phenols

Info

Publication number: GB2120656A
Application number: GB08308618A
Authority: GB
Inventors: Hans Dressler; Robert W Maxwell
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1982-05-26
Filing date: 1983-03-29
Publication date: 1983-12-07
Also published as: FR2527603B1; IT8348372A0; DE3313440A1; GB8308618D0; JPH0313229B2; DE3313440C2; IT1172263B; CA1242218A; JPS58216153A; GB2120656B; FR2527603A1

Abstract

A process for producing a thio- bis-phenol comprises reacting the corresponding phenol with sulphur dichloride in a solvent medium in the presence of a carboxamide. The carboxamide acts as a catalyst and is, for example, an N,N- dialkylcarboxamide having the formula: <IMAGE> where R1, R2 and R3 are various substituents, or R1 may be hydrogen.

Description

SPECIFICATION Preparation of thio-bis-phenols This invention relates to a process for preparing thio-bis-phenols by reacting phenols with sulphur dichloride. The term "phenol" is used herein in a generic sense to mean a compound in which at least one hydroxy group is attached to an aromatic nucleus, usually a benzene nucleus.

Generally, thio-bis-phenols are prepared by the condensation of the corresponding phenol with sulphur dichloride. For example, 4,4'-thio-bis(3-methyl-6-tert-butylphenol) is made by the condensation of 3-methyl-6-tert-butylphenol (i.e. monobutyl-m-cresol) with sulphur dichloride, SCI2, in an organic solvent. Past experience has shown the preferred solvents for carrying out the reaction to be aliphatic hydrocarbon solvents and the expected yields to be in the range of 65 to 70% of the theoretical yield. The compound 4,4'-thio-bis(3-methyl-6-tert-butylphenol) is a well known, valuable antioxidant for rubber and plastics.

According to the present invention there is provided a process for preparing a thio-bis-phenol, which comprises reacting a phenol with sulphur dichloride in the presence of a carboxamide.

It has now been found, surprisingly, that the addition of a catalytic amount of a carboxamide to the reaction charge of the phenol or hydroxybenzene and sulphur dichloride improves the in-hand yield of the desired thio-bis-phenol without affecting the quality of the product.

In accordance with an embodiment of this invention, the phenol is dissolved in an organic solvent and then reacted with sulphur dichloride in the presence of a catalytic amount of an N,Ndialkylcarboxamide. The reaction may, using as an example the starting material 3-methyl-6-tertbutylphenol, be generally expressed as:

CH3 CH3 CH3 2 HO))H3) + SC12 N,N-dialkylcarboxamide, HO > S W OH + 2HC1 C(CH3) C(CH3)3 C(CH3)3 A wide range of phenols such as cresois, resorcinols and alkylated derivatives may be used as starting material.Typical products produced include: (a) when the starting material is a monoalkylphenol, a product having the formula:

(b) when the starting material is a dialkylphenol, a product having the formula:

(c) when the starting material is an alkylated resorcinol, a product having the formula:

The R groups with respect to their positions on the respective aromatic nucleus and the sulphur linkage between the aromatic nucleii are shown as being randomly located, the R groups being the alkyl group or groups associated with the alkylated phenol and the actual location being a function of the location of the group or groups R in the starting material.

Typical thio-bis-phenols that may be produced include: 4,4'-thio-bis(2,6-di-tert-butylphenol), 4,4'-thio-bis(2,6-di-sec-butylphenol), 4,4'-thio-bis(6-tert-butyl-m-cresol), 2,2'-thio-bis(6-tert-butyl-4-ethylphenol The preferred carboxamides that are the catalysts in the present invention are known compounds which are commercially available or readily made by known methods and which are represented by the following formula:

wherein R, is hydrogen, alkyl, cycloalkyl, aralkyl, lower alkoxy or lower dialkyl amino, wherein R2 and R3 are the same or different and each is alkyl or aralkyl, and wherein, in the alternative, any two of R1, R2 and R3 are common members of a heterocyclic ring which contains the carboxamide nitrogen atom.

The preferred catalysts are N,N'-disubstituted carboxylic acid amides. They may be derived from lower fatty acids such as formic acid and acetic acid, as well as from higher fatty acids such as lauric acid. Obviously, amides of fatty acids with a medium number of carbon atoms, for example up to 7 carbon atoms, are also suitable. Among the fatty acid amides those derived from fatty acids having up to 4 carbon atoms usually give the best results. Besides fatty acid amides, there may also be used the acid amides or araliphatic carboxylic acid such as phenylacetic acid. Finally there may also be used amides of cycloaliphatic carboxylic acids such as hexahydrobenzoic acid.

Suitable catalysts may on the other hand be derived from aliphatic, araliphatic amines and from polymethylene imines. Of the alkyl-substituted amines those with substituents with up to about 4 carbon atoms and especially those containing ethyl or methyl groups are preferred.

The term "lower" herein usually denotes a radical containing up to about 4 carbon atoms, but also includes a radical containing up to 6 carbons or up to 8 carbon atoms or up to 10 carbon atoms.

Acid amides derived from cycloaliphatic imines with 5 to about 7 ring members are also well suited as catalysts.

Lactams, such as pyrrolidone, caprolactam and oenanthic lactam, N-substituted by lower alkyl radicals, especially by ethyl or methyl radicals, may also be used as catalysts. Alkyl-substituted compounds and especially the compounds substituted by lower alkyl radicals are preferred.

in general the best results are achieved with catalysts which are derived from formic acid on the one hand and from lower aliphatic secondary amines or from cycloaliphatic mines with 5 to 7 ring members on the other hand, and also with lactams N-substituted by lower alkyl radicals.

Suitable catalyst are for example: N,N-dimethylformamide, N,N-diethylformamide, N,Ndibutylformamide, N-formylpiperidine, N,N-diethylacetamide, N-acetylpyrrolidine, N,Ndimethylpropionamide, N,N-dimethylstearic acid amide, N-methylpyrrolidone, N-ethylcaprolactam, N,N-dimethylbenzamide, N-formylpyrrolidine, N-formylhexamethylene imine, N,N'-diformylpiperazine, N,N-dicyclohexylformamide, butyric acid piperidine, butyric acid dipropylamide, isobutyric acid diethylamide, hexahydrobenzoic acid dimethylamide, lauric acid dimethylamide, and Ncyclohexylpyrrolidone.

The catalytic amount of carboxamide is usually from 0.1% to 10% based on the weight of the phenol. Less than 0.1% of the carboxamide might not produce a noticeable effect. More than 10% of the carboxamide might cause little if any further yield improvement. The preferred amount of carboxamide to be used is about 0.2% to 2.0% by weight based on the weight of the phenol.

The reaction is usually carried out in a liquid medium. The organic solvents commonly used for dissolving the phenol and the catalyst include, for example, aliphatic hydrocarbons such as butane, pentane, hexane, iso-hexane, heptane, iso-heptane, octane and iso-octane, and alicyclic hydrocarbons such as cyclopentane, cyclohexane and methylcyclohexane. Solvent mixtures are also suitable.

Halogenated hydrocarbons, aromatic hydrocarbons, ethers and esters can also be used, as long as they are inert to sulphur dichloride and to the carboxamide catalysts. The amount of solvent to be used generally ranges from 0.5 to 10 parts by volume and preferably from 2 to 5 parts by volume per part by weight of the phenol.

Preferably, stoichiometric amounts of the reactants are used, i.e. 1 mole of sulphur dichloride is reacted with 2 moles of the phenol. Usually, the amount is from 0.8 to 1.2 moles of sulphur dichloride per 2 moles of phenol.

The sulphur dichloride and the phenol react exothermically. The temperature can be readily controlled by, for example, agitation of the reactant, dilution of the reactant, slow addition of the sulphur dichloride and external cooling. The reaction may be carried out in a wide range of temperatures and pressures, for example, at O-850C, preferably at 25-450C, and at atmospheric pressure.

Pressure has little effect, except possibly to hinder the removal of the HCI formed during the reaction. The lower the temperature, of course, the slower but the more seiective the reaction; higher temperatures can lead to undesirable side reactions. It is preferred to carry out the reaction at a temperature of 1 5-250C and at atmospheric pressure until the reaction is substantially completed and, optionally, to then heat the reaction to reflux and continue the reaction under reflux conditions until the evolution of HCI ceases.

The starting materials should preferably be charged to the reactor in the following order. The sulphur dichloride is dissolved in an organic solvent and added drop by drop at a controlled rate to a solution comprising the phenol and the carboxamide dissolved in the organic solvent so that the hydrogen chloride gas which results from the reaction is evolved continuously.

After the reaction is completed, the reaction mass may be cooled to a temperature of 0--250C.

The precipitate, which is the thio-bis-phenol, may be separated by filtration, washed with the organic solvent, then optionally with water and finally dried.

The invention is illustrated by the following Examples.

Example 1 A 2-litre flask equipped with a stirrer, a thermometer, a reflux condenser and a 500 ml addition funnel was charged with 212 g (1.24 moles) of commercial grade (96%) 3-methyl-6-tert-butylphenol dissolved in 633 g of n-hexane and 1.1 g of N,N-dimethylformamide (0.5% based upon the weight of the alkylated phenol) as a catalyst. A solution of 68 g (0.63 moles) of 96% sulphur dichloride in 1 59 g of n-hexane was added dropwise to the stirred flask contents over a period of 100 minutes, holding the reaction temperature at 20-250C. Hydrogen chloride gas was evolved soon after the start of the sulphur dichloride addition. The reaction mixture was stirred for 2 hours at 20-250C and sparged with nitrogen to sweep out the hydrogen chloride.Then the mixture was heated to reflux (630C) and held for 100 minutes at reflux to complete the condensation reaction. Next, the mixture was cooled to 20--25"C and filtered. The filter cake (282 g) was washed with 1128 g of n-hexane and filtered. The filter cake was washed again with 1 000 g of n-hexane and then spread on filter paper to air dry. The actual yield was 1 66 g (75.1% of theoretical) of 4,4'-thio-bis(3-methyl-6-tert-butylphenol) with a capillary melting point of 1 60CC and an off-white colour.

Example 2 A 500 ml flask equipped with a thermometer, a stirrer, an addition funnel, and a reflux condenser was charged with 33.3 g (0.2 moles) of commercial grade 3-methyl-6-tert-butylphenol (97%), 1 50 ml of n-hexane and 3.0 g (9 wt % based upon the weight of the alkylated phenol) of N,Ndimethylformamide. To the stirred solution was added over a period of 85 minutes at 1 9-250C and dropwise, a solution of 10.8 g (0.1 moles) of commercial grade sulphur dichloride (95%), hydrogen chloride being evolved soon after start of the addition. The stirred mixture was held at ambient temperature for another 68 minutes and at 24-460C for another 167 minutes, then cooled to 250C and filtered.The solid product was washed with 50 ml of n-hexane and 50 ml of water, then dried to give 29.1 g (81.3% of the theoretical yield) of 4,4'-thio-bis(3-methyl-6-tert-butylphenol) having a capillary m.p. of 1 58-1 590C and an off-white colour.

Example 3 Example 2 was repeated except that the catalyst was changed. Substituted for the N,Ndimethylformamide was 0.7 g (2 wt % based upon the weight of the alkylated phenol) of N,Ndimethylacetamide. The crude product was washed with n-hexane and dried to give 31.8 g (88.8% of the theoretical yield) of crude off-white 4,4'-thio-bis(3-methyl-6-tert-butylphenol).

Example 4 To a stirred slurry of 1 33.2 g (0.6 moles) of 4,6-di-tert-butylresorcinol in 500 ml of n-heptane was added 2.7 g of N,N-dimethylformamide (2 wt % based on the dibutylresorcinol). Then a solution of 34.5 g (0.3 moles) of 75% sulphur dichloride in 100 ml of n-heptane was added over a period of 75 minutes while the temperature of the reaction mixture was maintained at 21-250C with a cold water bath. The mixture was stirred at 240C for another 2 hours, whereupon the evolution of hydrogen chloride began to lessen. At this point a slow stream of nitrogen was passed through the reactor to facilitate the removal of HCI. After another 90 minutes at 25--260C, the slurry was filtered, the filter cake was washed with two 50 ml portions of n-heptane and dried at about 100 C/50 Torr (mm Hg).

There were obtained 86 g (62% yield) of 2,2'-thio-bis(4,6-di-tert-butylresorcinol), m.p. 21 7-21 80C.

Claims

1. A process for preparing a thio-bis-phenol, which comprises reacting a phenol with sulphur dichloride in the presence of a carboxamide.

2. A process according to claim 1, wherein the phenol is an alkylated phenol.

3. A process according to claim 2, wherein the phenol is an alkylated resorcinol.

4. A process according to any of claims 1 to 3, wherein the carboxamide has the general formula:

wherein R1 is hydrogen, alkyl, cycloalkyl, aralkyl, lower alkoxy or lower dialkyl amino, R2 and R3 are the same or different and each is alkyl or aralkyl, and wherein, in the alternative, any two of Ra, R2 and R3 are common members of a heterocyclic ring which contains the carboxamide nitrogen atom.

5. A process according to any of clairns 1 to 4, wherein the carboxamide is present in an amount of from 0.1 to 10% based upon the phenol.

6. A process according to any of claims 1 to 5, wherein the reaction is carried out in a liquid medium.

7. A process according to claim 6, wherein the liquid medium is a solvent medium which dissolves the phenol at least partially and the carboxamide, and which is inert to the sulphur dichloride.

8. A process for the preparation of 4,4'-thio-bis(3-methyl-6-tert-butylphenol), which comprises reacting 3-methyl-6-tert-butylphenol with sulphur dichloride in a hexane in the presence of N,Ndimethylformamide or N,N-dimethylacetamide until the evolution of hydrogen chloride ceases, cooling the reaction mass, and separating the precipitated 4,4'-thio-bis(3-methyl-6-tert-butylphenol) therefrom.

9. A process for the preparation of 2,2'-thio-bis(di-tert-butylresorcinoi), which comprises reacting 4,6-di-tert-butylresorcinol in heptane with sulphur dichloride in the presence of N,Ndimethylformamide until the evolution of hydrogen chloride ceases, and then separating the resulting 2,2'-thio-bis(di-tert-butyl resorcinol) therefrom.

10. A process for the preparation of a thio-bis-phenol, substantially as described in any of the foregoing Examples.

11. A thio-bis-phenol prepared by a process according to any of claims 1 to 10.